The invention relates to an electric rotating machine for turbine generators or the like, and, more particularly, to the cooling construction of a rotor for the electric rotating machine.
In electric rotating machines, ventilation and cooling for a rotor therein are effected by a construction in which axial flow passages are provided in the rotor to permit a cooling gas to flow through the rotor. With such a construction, the pressure loss becomes exceedingly great since the flow passages are rapidly reduced in area at the inlet portions thereof, through which a cooling gas flows into the axial flow passages. Accordingly, reduction of the pressure loss at the inlet portions of the axial flow passages becomes important in providing high efficiency cooling in the rotor. Japanese Patent Laid-Open No. 150898/1999 describes a method of reducing the pressure loss at inlet portions of such axial flow passages. With such an arrangement, rounding R is applied directly to corners it the inlet portions of the axial flow passages or rounding R is applied to the edges of guide plates or spacing pieces provided between axial flow passages. Thereby, separation in the flow is reduced at the inlet portions of the axial flow passages, so that the pressure loss can be reduced at the inlet portions.
The prior approach described above offers the following problems.
A first problem is the magnitude of the effect in reduction of the pressure loss. In the case of rounding R being applied directly to the inlets of the axial flow passages, a large rounding R actually applied cannot be so large because to do so it is necessary to increase the circumferential width of the rotor iron core to some extent at the inlets of the axial flow passages from the point of view of strength. Also, in the case of rounding R being applied to guide plates or spacing pieces, a rounding R larger than a circumferential spacing of the axial flow passages cannot be applied, in particular, in an electric rotating machine having a large capacity, in which the circumferential spacing of the axial flow passages is small. Therefore, any great effect in reduction of pressure loss cannot be expected because it is not possible to decrease the rate of change in the flow passage area in a flow direction.
A second problem is related to cost. In the case of the rounding R being applied directly to inlets of the axial flow passages, a processing is necessary for applying rounding R to each of the multiplicity of inlets of the axial flow passages provided circumferentially, which involves an increased cost for processing. In the case of the rounding R being applied to guide plates or-spacing pieces, the material cost and processing cost will be correspondingly increased.
It is an object of the present invention to provide an electric rotating machine which has a construction for cooling the a rotor thereof, and which is low in cost and is greatly effective in reduction of the pressure loss.
To attain the above-mentioned object, the invention has a first feature which resides in an electric rotating machine having axial flow passages for cooling an interior of a rotor, in which inlet flow passages leading to the axial flow passages are composed of convex portions formed on surfaces of a rotor spindle between and below the rotor coil ends, and concave grooves are formed between the convex portions, and the convex portions are tapered to have a height increasing toward a downstream side.
More preferably, the axial length L of the convex portions is greater than the radial difference between the positions of a maximum radius R2 and a minimum radius R1 of the convex portions.
Bottom surfaces of the concave grooves are effectively tapered to have a height increasing toward the downstream side.
Further, a minimum radius portion of the inlet flow passages leading to the axial flow passages may have a diameter smaller than that of a minimum radius portion inside the axial flow passages.
The invention has a second feature which resides in an electric rotating machine having axial flow passages for cooling an interior of a rotor, the machine comprising inlet flow passages leading to the axial flow passages, and wherein the inlet flow passages gently decrease in flow passage area in an axial direction so that points of inflection are not produced on a curve connecting flow velocity distributions in a widthwise direction of the flow passages at portions immediately after inflowing into the axial flow passages.
The invention has a third feature which resides in an electric rotating machine comprising axial flow passages for cooling an interior of a rotor, wherein a minimum radius R4, of upstream side portions of the axial flow passages are smaller than a minimum radius R3 of an interior of the axial flow passages on a downstream side thereof. Thus, the pressure loss can be reduced because a substantial area of the flow passages, at portions immediately after the inflow of cooling gas into the axial flow passages, can be made large.
The invention has a fourth feature which resides in an electric rotating machine having axial flow passages for cooling an interior of a rotor, the machine comprising inlet flow passages leading to the axial flow passages and composed of flow passage forming members formed on surfaces of a rotor spindle between and below rotor coil ends, and concave flow passages formed between the flow passage forming members, the flow passage forming members being tapered to have a height increasing toward a downstream side.
Hereupon, spacing pieces may be provided between the rotor coil ends, and the flow passage forming members may be constructed to be integral with the spacing pieces.